Anodic Hydrogen Electrode Reaction in Aluminum Chloride-1-Ethyl-3-methylimidazolium Chloride Ionic Liquids

Abstract

The anodic hydrogen electrode reaction was examined in the Lewis acidic 66.7-33.3 mole percent (m/o) aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl₃-EtMeImCl) ionic liquid and the LiCl-buffered neutral AlCl₃-EtMeImCl ionic liquid containing LiAlH₄. Raman spectroscopy experiments revealed that the Al₂Cl₇⁻ anion in the acidic ionic liquid is directly involved in the dissolution of the LiAlH₄. Electrochemical hydrogen generation was verified by gas chromatography and XRD for Pd and Ti electrodes polarized in the ionic liquid. The hydrogen electrode reaction was irreversible, i.e., it followed an E_irC_ir mechanism in the 66.7 m/o ionic liquid at 298 K. However, it was quasireversible in the LiCl-buffered ionic liquid at 353 K and appeared to follow an E_qrC_ir mechanism.